The shaping of the cleaved end of an optical fiber has been previously described, e.g., in the form of micromachined focusing elements (M. Sasaki et al., Direct photolithography on optical fiber end, Jpn. J. Appl. Phys. 41, 4350-4355 (2002); P. N. Minh et al., Batch fabrication of microlens at the end of optical fiber using self-photolithography end etching technique, Opt. Rev. 10, 150-154 (2003); F. Schiappelli et al., Efficient fiber-to-waveguide coupling by a lens on the end of the optical fiber fabricated by focused ion beam milling, Microelectronic Eng. 73-74, 397-404 (2004); R. S. Taylor and C. Hnatovsky, Particle trapping in 3-D using a single fiber probe with an annular light distribution, Optics Express 11, 2775-2782 (2003); C. Liberale et al., Miniaturized all-fiber probe for three-dimensional optical trapping and manipulation, Nature Photonics 1, 723-727 (2007).), optical antennas (E. J. Smithe, E. Cubucku, and F. Capasso, Optical properties of surface Plasmon resonances of coupled metallic nanorods, Optics Express 15, 7439-7447 (2007).) or movable mechanical structures (fiber-top technology, D. Iannuzzi et al., Monolithic fiber-top sensor for critical environment and standard applications, Appl. Phys. Lett. 88, 053501 (2006).). The possibility to shape the cleaved end of an optical fiber represents a fascinating opportunity for the development of new devices for a wide variety of applications, including photonics, optical trapping, biochemical sensing (D. Iannuzzi et al., A fiber-top hydrogen sensor, Sensors & Act. B121, 706-709 (2007).), and atomic force microscopy (D. Iannuzzi et al., Fiber-top atomic force microscope, Rev. Sci. Instr. 77, 106105 (2006).). Unfortunately, the advantages offered by those instruments may be hampered by the large costs of production, which can be due to the fact that, at present, there are no known versatile fabrication procedures for batch manufacturing of arbitrary micromachined parts on the facet of optical fibers.
Optical lithography is one of the most widespread micromachining processes in silicon based technologies such as integrated circuits and MicroElectroMechanical Systems (See for example G. T. A. Kovacs, Micromachined transducers sourcebook (McGraw-Hill, New York, 1998).). The application of this process for the fabrication of patterns on top of optical fibers requires a precise alignment of the lithography mask to the centre of the fiber, which is a too cumbersome operation if standard photolithography mask aligners are to be used. On the other hand, over the last decades, the need of quick and reliable optical fiber fusion splicing machines, triggered by the fast growth of the telecommunication industry, has pushed enormous progress in the development of opto-mechanical tools that align the cleaved ends of two opposite optical fibers. Most of commercially available optical fiber fusion splicing machine use simple image-based active fiber alignment techniques to bring the two ends of the fibers in contact automatically within a few seconds (A. D. Yablon, Optical fiber fusion splicing (Springer, Berlin, 2005).).